Refining unsaturated acids and esters



UNITED STATES PATENT OFFICE EWING UNBA'I'URATID ACIDS AND Isms Ralph E. III, In. leles, Calif.

No Drawing. Application April Serial 80. 587,611

14 Clllma. (Cl- 200-419) This invention relates to the refining and decolorizing of high molecular weight organic acids and corresponding esters, and has for its general object to provide an improved process whereby the components to be extracted from the material treated, may be removed more economically and to better advantage in the several respects later discussed, than by the usual or known methods and reagents.

At the outset it should be understood that the invention is applicable generally to the treatment of organic acids herein defined as including visi'ble or latent color body-containing fatty acids, natural resin acids, the esters of such acids, or mixtures thereof. As will be understood, the organic acid mixtures to be treated may contain other compounds or impurities of a nature depending upon the type and source of the material. Illustrative organic acid mixtures of the character capable of being refined and decolorized in accordance with the invention, include the following:

Reacidulated soap-stock, a mixture of fatty acids, together with or without fatty acid esters and other substances naturally present in the original crude fat, which mixture is produced when fat refining soap-stock is treated with mineral acids for the purpose of decomposing soap present in the refining soap-stock.

Refining soap-stock is a soap-containing mixture which settles out or which is washed out of a fat during the process whereby a crude fat is treated with alkaline compounds for the purpose of removing free fatty acids or the various color constituents normally present in crude fats, the object of which operation is that of refining the original crude fats.

Petroleum fatty acids. 1. e. those organic acids which are products of the limited oxidation of high molecular weight petroleum hydrocarbons such as petroleum white oils, petrolatum and paraiiin wax.

Tall oil comprises a mixture of components including fatty acids and resin acids together with some non-acid constituents, which mixtureis a by-product of sulphate or kraft paper manufacture and is obtained by acidification of the black liquor soap. which is salted out and rises to the surface of the black liquor on standing. The non-acid constituents consist of various hydrocarbons, esters and lecular weight cyclic alcohols.

There are known processes of refining of crude tall oil. crude petroleum fatty acids, and other crude fatty acids produced from reacidifying may also contain high mo- 2 saponified fats whereby the aforesaid organic acids are first dissolved in solvents inert to sulphuric acid and the solution thus obtained is subsequently treated with sulphuric acid as a refining agent.

I am also aware of U. 8. Patent 2,038,617 which describes a process for refining crude fatty acids in petroleum hydrocarbon solution by means of concentrated phosphoric acid of preferably about 80% to 90% or 95% strength.

When desired to refine dark colored organic mixtures by these and other known methods, it has been necessary to dilute the mixtures with solvents that are indifferent to the refining reagents to be employed. After the refining step, it has been necessary to remove the solvent by distillation or other means. This procedure is uneconomical in practice since a considerable expenditure of heat energy must be consumed for the sole purpose of eliminating the carrying solvent from the refined product. In accordance with the invention it is now made possible to obviate the use of any solvent other than the aqueous inorganic acid mixture itself. and in so do ng to maintain both effective action of the acid mixture on the stock being treated, and separation of the resulting sludge from the treated stock.

Heretofore, the conventional processes employing sulphuric acid as the treating agent, have resulted in the formation of substantiallv solid sludges which, because of their granular formation, tend to retain and prevent separation of appreciable quantities of the treated product material. Also, sulphuric acid reagents, used alone, tend to create various side reactions and oxidizing efl'ects detrimental to the treatment and which desirably should be prevented or suppressed.

These disadvantages are overcome by the invention through the use of a treating reagent, the composition of which may be adjusted to produce a completely liquid sludge which retains no appreciable amount of the product material. Also the reagent, though containing sulphuric acid, is so constituted as to inhibit or suppress, by virtue of the pressure of phosphoric acid, the detrimental side reactions and oxidizing effects normally encountered in treatments with sulphuric acid.

I have discovered that these and other desirable objects can be accomplished by using a refining agent of inorganic nature, comprising a mixture of phosphoric acid, sulphuric acid and water. Each substance named shall be devoid of either of the other two components for the purpose of calculation, although they may contain minute quantities of other impurities suchas are commonly present even in chemically pure grades oi these materials. The results and refining eflects of the sulphuric and phosphoric acid mixture are characteristically different in many respects from those resulting from the use of sulphuric and phosphoric acid solutions alone. Conizing efliclency and often in subsequent color reversion of the decolorized material in storag with the result that the product gradually darkens and may eventually become even darker than the color of the original crude material which was treated.

I have discovered that when sulphuric acid, water, and phosphoric acid, each considered at substantially 100% purity, are mixed together in proportions within the hereinafter defined range, and the mixture thus prepared is used as a refining reagent, undesirable sulfonation reac--" tions are suppressed or maybealtogeth'er elimi- By the use of the present combination nated, so that the refined products are not susceptible to color reversion instorage. Color bodies originally presentin the crude material will be substantially totally removed from the crude material by the refining reagent in liquid phase, as a result of selective solvent action of the reagent upon color bodies both visible and latent and without substantial solvent action by the reagent upon the uncolored organic acids which comprise the mixture. Sulphuric acid, used alone as a refining agent either in highly concentrated or slightly diluted condition, appears to attack oxygenated and hydroxylated substances first, with the formation of esters or sulfated compounds. Also or subsequently, sulphuric acid attacks other unsaturated organic compounds that may be present with the formation of sulfated or sulfonated comprincipal proportion of the crude pounds. The products of reaction with sulphuric acid are relatively stable and more often than not are also of very dark color and are at the same time very difiicult to remove from other unreacted substantially uncolored organic compounds present. The present phosphoric and sulphuric acid combination however seems to have a preferential dissolving action upon the colored oxygenated substances as well as the hydroxyl- .ated substances. Whether or not this solvent action involves a solution association of the acids or is the result of inter-reaction by the oxygencontaining materials with the phosphoric acid or the acid mixture, is not clear. However, regardless of the exact mechanism of the solvent action or reaction, the solution of visible and latent coloring materials thus produced is readily decomposed by dilution with substantial proportions of water, with the result that the phosphoric acid and the color bodies or latent color bodies may be subsequently recovered in apparently substantially unchanged condition.

As previously mentioned, selective 'action of concentrated phosphoric acid solutions alone upon the visible and latent color bodie is impractical at large proportions relative to the material being refined. 0n the other hand, the action of sulphuric acid is so vigorous that extremely small proportions of concentrated sulphuric acid relative to the material being refined will effect a distinct refining action, but because of its vigor and of the undesirability of the above mentioned side reactions, refining by means of sulphuric acid is very difficult to accomplish satisfactorily except in the presence of substantial proportions of diluting solvents inert to the acid. of the acids, it is possible to effect a ready and relatively complete separation of the treated stock and sludge phases, significantly without necessitating the use of diluents or other solvents, and at relatively low reagent and treating costs entirely warranted by the results.

Sulphuric acid, either concentrated or partially diluted by water, when used as the refining reagent, will associate in some fashion with visible or latent color bodies and produce a somewhat granular, solid or nearly solid sludge, separation of which from the main bulk of the material is conveniently efiected only at the expense of the main bulk as a result of an entrainment of organic liquid substances between the solid or semi-solid particles, thus complete separation of the liquid and solid components can be effected only by the use of selective solvents. Using the present reagent, and without other solvent, complete gravity separation of the extracted bodies occurs in a sludge that is liquid at least in considerable part, and preferably substantially entirely liquid. In general, and other conditions being equal, formation of more liquid or fluid sludges is favored by increased proportions of phosphoric acid in the reagent, and decreased proportions of water.

The invention contemplates the use of reagents of compositions within the range of a minimum of 15% phosphoric acid and a maximum of sulphuric acid, the ratio of the two acids being expressed on a water-free basis. Greater concentrations of phosphoric acid, 1. e. above the 15% lower limit, are to be desired, and from the standpoint of the refining or reagent efllciency it is preferred to use a higher percentage of phosphoric acid than of sulphuric acid in the reagent. The exact composition in any given instance may of course be adjusted to suit the requirements of the particular stock being treated.

As to the water content of the solution, it is contemplated that the maximum amount of water will be that quantity equivalent to the water contained .in at least a concentrated solution of the (pure) phosphoric acid contained in the reagent, plus three molecules of water for each molecule of sulphuric acid in the reagent. For most efllcient results in the average treatment, I prefer to limit the water content to that quantity contained in at least a 95% concentrated solution of the phosphoric acid content, plus one molecule of water for each molecule of sulphuric acid in the reagent. Otherwise stated, the water content of the reagent will be not substantially in excess of 24%, by weight of the reagent, and preferably will be considerably below that proportion.

Within the broader ranges specified, the prefen-ed reagent compos tion, tak ng into account its efllciency, the desired separability of the treated stock and sludge phases, the desired liquid consistency of the sludge, and the adaptability of the reagent for the treatment oi. difierent organic acid stocks, is one in which the phosphoric acid is present in an amount of 30-65%, by weight, oi the total phosphoric and sulphuric acid content (on an anhydrous basis), and the water is from 3 to by weight, of the phosphoric acid,

sulphuric acid and water solution. With further reference to the water content of phosphoric acid and sulphuric acid solutions within the broader range specified, or within the last discussed preferred range, it is contemplated that in the treatment of some stocks, depending upon their composition and response to the reagent treatment, the reagent may be substantially anhydrous.

In speaking of the desirability. generally, of forming a sludge that is completely fluid or essentially liquid, it will be understood that the composition of the reagent may be adjusted within the defined limits, to so determine the physical nature of the sludge. It may be observed;how-

ever, that if desired, some granulation may be permitted in the sludge, so long as the soid bodies.

or granules are filled inbetween with a liquid sludge phase that displaces the treated material out of the sludge body.

While in the foregoing, reference has been made to the fact that by virtue of the effect of both phosphoric and sulphuric acid in the reagent, and in the proportion specified, it is possible to efi'ect satisfactory gravity separation of the sludge and treated organic acid components. it will be understood that the invention does not preclude the use of a suitable solvent or diluent,

such as naphtha. Thus the solvent may be in- .troduced to or incorporated in the organic acid and reagent before or during the treatment. Thereafter, complete separation of the sludge from the treated material may be effected without the use of clay. or particular advantage in expediting the complete process, may be the introduction of the solvent to the mixture after the acid solution treatment and as a diluent to enhance complete separation of sludge particles.

Ordinarily, when no diluent or solvent is used, it may be desirable to effect complete removal of all sludge particles by filtering or passing the refining process, the fol'owingexamples arecited. These examples are not to be construed as limitin: the variations which may be utilized but are given only as illustrative examples.

The color grading numbers are in accord with the color grading system of the 1933 color standards of the National nish, and Lacquer Manufacturers, which system is useful for specifying the optical color density of clear transparent liquids.

, Example 1.Three hundred gram specimens of crude tall oil, having an original color of 18 plus, were treated with a refining reagent composed of 34% anhydrous orthophosphoric acid (H.1PO4) and 66% sulphuric acid mono-hydrate (H2SO4H2O). Various proportions of the refining reagent were utilized in respective samples as stated in the following table. The refining reagent was mixed with the crude tall oil at a temperature of 125 FL,v the mixture stirred rapidly for thirty minutes, following which the fluid sludges were allowed to settle out at a temperature of 140-150 F. The sludges were drawn off in fluid condition and the residual stock was clarified by contacting it with 10% of its weight of activated bleachin clay, at a temperature of 240-250 F. The bleaching clay was removed by filtration and the refined products thus obtained were of the colors designated by the table.

Volume per cent of re fininglreage it base g g l on t e v0 ume of original stock product M a a 12-13 12-13 1 12-13 g g i243 Example 2.Using the same procedure as in Example 1, specimens of crude tall 011 were treated with refining reagents consisting of orthophosphoric acid of 96-97% strength, mixed in I several different ratios with sulphuric acid of 93% strength (2H2SO4.H2O), the proportions of the phosphoric acid and the sulphuric acid were as given in the following table. A constant ratio of the sulphuric acid in the reagent mixture, relative to the weight of stock being refined, was maintained at 2 Reagent Composed oi A B O D E F G H I J K PhosphoricAcid 0 l0..... 20 3O 70 B0 90 100. Sulphuric Acid (heml- 100 90 80 70 60 50 40 30 20 l0 0.

hydrate) (211 8041110).

Rate of sludge setting..-.. 811533 at}? $10 Rapid. Rapid.... Rapid-.-. Rapid.... Rapid. Rapid.- Rapid Rapid- Rapid.

l ICU Condition of sludge Crumbly.. Solid F l u i d F l u i d F l u i d Viscous Liquid. Liquid. Liquid Liquid. Liquid.

cake v e r v Viscous. Viscous. Liquid.

Viscous Coloroifinishedproduct.. l8 l7l8. 16+ 16+ 17 l6+.... 1B 16 l6 17+.

treated material through natural or activated clays of the type commonly employed. If on the other hand solvent is used according to any of the procedures indicated, the sludge separation may be completed without the use of clay.

The ratio of the reagent used to the quantity of stock treated, may vary within wide limits depending upon the composition of the stock, particularly with respect to its content of color bodies to be extracted by the reagent. As illustrative, the proportion, by volume, of reagent to stock, may fall within the range of 0.1% to 25%.

In explanation of the operation of the present In the absence of sulphuric acid (K in the above table) the amount of phosphoric acid used corresponds to 25% of the weight of the treated stock. While productive of rapid settling and a treated material of good color, the refining action of the phosphoricacid alone was found to be less positive than with reagents containing sulphuric acid. a

Example 3.-Three hundred grams of reacidulated soap stock of color 17 obtained from sardine oilrefining soap stock, was treatedwith 15 milliliters of a refining reagent consisting of 55 parts phosphoric acid and 45 parts sulphuric acid Association of Paint, Var-.

, 7 mono-hydrate (318041130). The temperature of treatment was 125-130 I". The sludge settled out as a thick fluid and was drawn oil. After treatment of the residual upper layer by activated bleaching clay and filtration the final product had a color of 7.

, esters oi said acids for the removal of color bodies,

that includes contacting said mixture with a solution of phosphoric acid and sulphuric acid, the proportion (on an anhydrous basis) individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the total phosphoric and sulphuric acid content.

2. The method of refining a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids for the removal of color bodies, that includes contacting said mixture with an aqueous solution of phosphoric acid and sulphuric acid, the proportion (on an anhydrous basis) individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the total phosphoric and sulphuric acid content.

3. The method of refining a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids for the removal of color bodies, that includes contacting said mixture with an aqueous solution of phosphoric acid and sulphuric acid, the proportion (on an anhydrous basis) individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the total phosphoric and sulphuric acid content, and the water content of the solution being not substantially in excess of 24%, by weight, of the solution.

4. The method of refining a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids for the removal of color bodies, that includes contacting said mixture with a hydrous solution of phosphoric acid and sulphuric acid, the proportion (on an anhydrous basis) of phosphoric acid in the solution being between about 30% to 60% of the total phosphoric and sulphuric acid content.

5. The method of refining a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids for the removal of color bodies, that includes contacting said mixture with an aqueous solution of phosphoric acid and sulphuric acid, the proportion (on an anhydrous basis) of phosphoric acid in the solution being between about 30% to 60% of the total phosphoric and sulphuric acid content, and the water content being not substantially in excess of 24%, by weight, of the solution.

6. The method of refining a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids for the removal of color bodies, that includes contacting the mixture with a prepared solution consisting essentially of phosphoric acid, sulphuric acid and water without otherwise appreciably diluting the mixture, the

proportion (on an anhydrous basis) individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the phos phoric and. sulphuric acid content of the solution.

7. The method of refining a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids 'for theremoval of color bodies, that includes contacting the mixture with a prepared aqueous solution consisting essentially of phosphoric acid and sulphuric acid without otherwise appreciably diluting the mixture, the proportion (on an anhydrous basis) individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the phosphoric and sulphuric acid content of the solution, and the water content of the solution being not substantially in excess of 24%, by

weight, of the solution, and separating the resulting acid sludge from residual insoluble organic acids.

8. The method of refining a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids for the removal of color bodies, that includes contacting the mixture with a substantially anhydrous solution of phosphoric acid and sulphuric acid, the proportion individually of phosphoric acid and sulphuric acid in the solution being in excess of 15% of the total quantity of said acids in the solution.

9. The method of refining a mixture of unsaturated acids of the class consistingof higher aliphatic fatty acids, natural resin acids and esters of said acids for the removal of color bodies, that includes contacting said mixture with an aqueous treating solution of phosphoric acid and sulphuric acid, the proportion individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the total phosphoric and sulphuric acid present, and the quantity of water in the solution being not substantially greater than the total water contained in at least a solution of the same quantity (on an anhydrous basis) of the phosphoric acid in said treating solution plus one molecule of water for each molecule of sulphuric acid in the treating solution.-

10. The method of refining for color body removal a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids, which if treated with aqueous sulphuric acid alone to remove the color bodies would produce a granular sludge, that includes contacting said mixture with an aqueous solution of phosphoric acid and sulphuric acid, the proportion (on an anhydrous basis) individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the phosphoric and sulphuric acid content, and thereby producing a substantially nongranular sludge.

11. The method of refining a mixture of unsaturated acids of the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids for the removal of color bodies, that includes contacting the mixture with a solution consisting essentially of phosphoric acid, sulphuric acid and water without otherwise appreciably diluting the mixture, the proportion (on an anhydrous basis) individually of phosphoric acid asaaeeo 9 content of the solution, thereai'ter diluting the resulting treated organic acids and sludge with a solvent, and then separating the treated organic acids. sludge and solvent.

12. A color body extracting reagent for the treatment of unsaturated acids 0! the class consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids, comprising a solution of phosphoric acid and sulphuric acid, the proportion (on an anhydrous basis) individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the total phosphoric and sulphuric acid present.

13. A color body extracting reagent for the treatment oi unsaturated acids of the clas consisting of higher aliphatic fatty acids, natural resin acids and esters of said acids, comprising a solution 0! water, phosphoric acid and sulphuric acid, the proportion (on an anhydrous basis) individually oi'phospboric acid and sulphuric acid in the solution being not less than 15% of the total phosphoric and sulphuric acid present. and the water content oi the solution being not substantially in excess of 24%, y weight, of the solution.

acid and sulphuric acid, the proportion (on an anhydrous basis) individually of phosphoric acid and sulphuric acid in the solution being not less than 15% of the total phosphoric and sulphuric in acid content.

RALPHH. HUFF.

REFERENCES CITED The following references are oi record in the 15 the of this patent:

UNITED STATES PATENTS Number Name Date Hall Aug. 17, 1888 Freiburg July 3, 1934 Vesterdal Apr. 28, 1936 Gayer Dec. 3, 1940 Beller Feb. 4, 1941 

